on the light side

( However, it should not only have the maximum penalty raised but also consider setting a minimum penalty. In Hong Kong, the stiffest sentence drink drivers have been given is 32 months' imprisonment, which is half the maximum penalty. If punishments are on the light side, a higher maximum penalty will not be an effective deterrent.
)

If punishments are on the light side, a higher maximum penalty will not be an effective deterrent.


呢句的on the light side　點解？？？？